It is known that both room temperature and heat curable silicone rubbers have many outstanding properties which make them desirable for industrial applications, however, such cured organopolysiloxanes are extremely difficult to bond to other materials. As a result, an extensive amount of work has been heretofore done in developing primers and other coating materials which can be applied to the surface of the organopolysiloxane to aid in bonding the polysiloxane to other material. (See, for example, U.S. Pat. Nos. 3,455,762; 3,377,309; and 3,619,256.) While some degree of success has been obtained by approaches of this nature, all such approaches have an undesirable cost impact in that they require some additional material. Unfortunately, the characteristics of silicone rubbers that make them desirable for many applications are just the same characteristics that make it difficult for other materials to be bonded to silicone rubber. Further, silicone rubbers are outstandingly resistant to corona discharges, ozone, and high temperature oxygen which are the means by which other relatively inert polymeric materials are treated to increase their surface energy and therefore their bondability to other materials. According to this invention, I have found a technique for treating the surface of silicone rubbers which raises the energy of the surface to the point where it may be bonded directly to a wide variety of liquid crosslinkable polymers and a wide variety of adhesives. The direct bond with the crosslinkable polymers is extremely useful in rocket motor applications and the availability of a wide variety of adhesives will permit a greater choice of materials which may be bonded to the silicone rubber by the adhesives.
It is accordingly an object of this invention to provide a method for treating the surface of a silicone rubber to produce a high energy surface.
It is another object of this invention to provide a method for treating silicone rubbers that improves the bondability of the rubber with a wide variety of materials.
These and other objects of this invention will be readily apparent from the following description of the invention.